My co-pending application referred to hereinabove shows an on-line system for monitoring the color, opacity and brightness of a moving paper web within specified limits in the course of manufacture of the paper. The system includes an optical head having a multiplicity of detectors including four color tristimulus value sensing units and a central brightness sensing unit, all of which are oriented toward the same point, and an opacity sensing unit which is angularly oriented with reference to the axis of the central detector so as to be directed toward a point spaced downstream from the point at which the central detector is directed.
In use of the multi-detector head shown in my co-pending application, a black background must be provided for all of the color tristimulus and brightness detectors and a white background must be provided for the opacity detector. In addition, these detectors must be able to be separately calibrated with reference to standard black and white backgrounds.
I have invented an optical shoe assembly for a multiple detector optical head which requires spaced black and white backgrounds in use thereof. My optical shoe assembly permits of standardization of the optical head without removing the system from the line on which it is used. My optical head assembly is simple in construction and in operation for the results achieved thereby.
One object of my invention is to provide an optical shoe assembly for use with an optical head which requires spaced white and black backgrounds.
Another object of my invention is to provide an optical shoe assembly which permits of standardization of the head detectors without the necessity for removing the system from the line on which it is used.
A further object of my invention is to provide an optical shoe assembly which is simple in construction and in operation for the results achieved thereby.
Other and further objects of my invention will appear from the following description.
In general, my invention contemplates the provision of an optical shoe assembly for use with a multi-detector optical head in which the shoe assembly includes a frame for supporting a length of the web over a housing opening below which there is mounted a generally rectangular block, one side of which normally is positioned so as to be exposed through the housing opening with the edges of the side in sealing engagement with the edge of the housing opening. This first block side is provided with an optically black cavity over which a quartz shoe is mounted which shoe is provided with a transversely extending white background so that the side presents spaced white and black backgrounds for the portion of the web moving over the shoe housing. Other respective sides of the block carry a standard white background which may, for example, be a mirror and a black standard. A motor is adapted to be energized selectively to position the white standard and the black standard sides at the housing opening. Means is provided for pressurizing the housing during the period of time over which the standard sides are being moved into place so as to prevent the entry of foreign material into the housing.